Effect of large targeted deletions on the mitotic stability of an extra chromosome mediating drug resistance in Leishmania.

A mitotically stable linear extra chromosome obtained in a Leishmania donovani strain rendered mycophenolic acid-resistant has been physically mapped. This 290-kb chromosome has an inverted duplicated structure around a central inversion region, and is derived from a conservative amplification event of a approximately 140-kb subtelomeric end of chromosome 19. Large-sized targeted deletions of the central region were performed through homologous recombination using three specific transfection vectors. The size of the extra chromosome was thus successfully reduced from 290 to 260, 200 and 120 kb respectively. The mitotic stability of these chromosomes was then analysed in drug-free cultures over >140 days. Results differed according to the deletion created. By contrast with the smallest deletion the two largest deletions altered mitotic stability, leading to progressive loss of the size-reduced chromosomes with similar kinetics in both mutants. The 30-kb region common to both deletions may therefore be considered as involved in mitotic stability. A 44-kb contig covering this region could be assembled and sequenced. The analysis of this sequence did not reveal any sequence elements typical of centromeric DNA. By contrast, its enrichment in homopolymer tracts suggests that this region might contain an origin of replication.

Abilities of some tryptophan and phenylalanine derivatives to inhibit gastric acid secretion.

Benzotript (N-p-chlorobenzoyl-L-tryptophan) has been shown to be a receptor-antagonist in vivo and in vitro for peptides from the gastrin family. In the present study, we examine tryptophan, and some of its N- and C-acylated derivatives, as well as some phenylalanine derivatives, to show their ability to inhibit gastrin-induced acid secretion in the rat in vivo and to compete for the binding of [125I]-(Leu-15)-HG-17 to its cellular receptor on rabbit isolated gastric mucosal cells. N- and C- derivatives of tryptophan and phenylalanine were found to inhibit gastrin-induced acid secretion and binding of [125I]-(Leu-15)-HG-17 to its mucosal cell receptors. By either criterion, the relative antagonistic potencies of the compounds tested were: tert-butyloxycarbonyl-L-tryphophan-p-nitrophenyl ester approximately equal to tert-butyloxycarbonyl-L-tryptophan-carbamoylmethyl ester greater than tert-butyloxycarbonyl-L-tryptophyl-L-methionyl-carbamoylmethyl ester approximately equal to tert-butyloxycarbonyl-L-phenylalanine-carbamoylmethyl ester approximately equal to tert-butyloxycarbonyl-L-tryptophyl-L-methionyl-amide greater than tert-butyloxycarbonyl-L-tryptophan greater than tert-butyloxycarbonyl-L-phenylalanine greater than benzyloxycarbonyl-L-tryptophan approximately equal to benzotript, with minor differences between the in vivo and the in vitro experiments. These results demonstrate that both the nature of the amino acid residue and the N- and C-substitutions are important in determining antagonist activity and affinity for gastrin receptors.

Correlation between phospholipid breakdown, intracellular calcium mobilization and enzyme secretion in rat pancreatic acini treated with Boc-[Nle28, Nle31]-CCK-7 and JMV180, two cholecystokinin analogues.

In this work in vitro pharmacological profiles of two analogues of the C-terminal heptapeptide of cholecystokinin (CCK) were evaluated. The analogue Boc-[Nle28, Nle31]-CCK-7, a stable analogue of CCK-8, has the same activity profile as CCK-8, and was found to be very potent in stimulating amylase secretion, phospholipid breakdown and [Ca2+]i mobilization from rat pancreatic acini. It can be used as a probe for studying CCK-actions. The CCK-analogue Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethylester, (JMV180), which stimulates amylase secretion without inhibition at supramaximal concentrations, has different effects on phospholipid hydrolysis and [Ca2+]i mobilization, compared to CCK-8 and Boc-[Nle28, Nle31]-CCK-7. Compound JMV180 was unable to significantly promote phospholipid breakdown, and was only 50%-60% as efficacious as Boc-[Nle28, Nle31]-CCK-7 in promoting [Ca2+]i mobilization. These findings suggest that low affinity CCK-receptors might be responsible for the supra-maximal inhibition of amylase secretion, and are correlated with phospholipid breakdown and maximal [Ca2+]i mobilization.

Synthesis and biological activity of some partially modified retro-inverso analogues of cholecystokinin.

Syntheses of some partially modified retro-inverso analogues of the C-terminal octa- or heptapeptide of cholecystokinin are described. These analogues (in which the C-terminal carboxamide was deleted or not) were obtained by reverting one or several peptide bonds in the parent molecule. All these compounds were able to inhibit binding of labeled CCK-8 to rat pancreatic acini and guinea pig brain membranes and to stimulate amylase release from rat pancreatic acini with various potencies. Some of these derivatives reproduce only part of the biological response of CCK on amylase release.

Synthesis and biological activities of some pseudo-peptide analogues of tetragastrin: the importance of the peptide backbone.

Pseudo-peptide analogues of the C-terminal tetrapeptide of gastrin, in which a peptide bond has been replaced by a CH2-NH bond, i.e. (tert-butyloxycarbonyl)-L-tryptophyl-psi (CH2-NH)-L-leucyl-L-aspartyl-L-phenylalanine amide (8), (tert-butyloxycarbonyl)-L-tryptophyl-L-leucyl-psi (CH2-NH)-L-aspartyl-L-phenylalanine amide (13), (tert-butyloxycarbonyl)-L-tryptophyl-L-leucyl-L-aspartyl-psi (CH2NH)-L-phenylalanine amide (20), were synthesized. The pseudo-peptides 8 and 13 were shown to have the same affinity as (tert-butyloxycarbonyl)-L-tryptophyl-L-leucyl-L-aspartyl-L-phenylalanine amide (21) for the gastrin receptor on isolated mucosal cells. The pseudo-peptide 20 exhibited lower affinity (IC50 congruent to 10(-5) M). The biological activity of these pseudo-peptides was studied on acid secretion in the anesthetized rat. Compound 8 stimulated acid secretion, identically with that of 21. Compound 13 did not exhibit any agonist activity but was able to antagonize the action of gastrin (ED50 = 0.3 mg/kg). Compound 20 did not show any agonist activity but was able to inhibit gastrin-induced acid secretion, with lower potency (ED50 = 15 mg/kg). The importance of the peptide bonds in the mode of action of gastrin is discussed, and a hypothetical approach of the mechanism of action is presented.

Synthesis and biological activity of new peptide segments of gastrin exhibiting gastrin antagonist property.

A series of C-terminal peptide segments of gastrin, i.e., (tert-butyloxycarbonyl)-L-tryptophyl-L-methionyl-L-aspartic acid amide, (tert-butyloxycarbonyl)-glycyl-L-tryptophyl-L-methionyl-L-aspartic acid amide, (tert-butyloxy-carbonyl)-L-tyrosyl-glycyl-L-tryptophyl-L-methionyl-L-asp artic acid amide, and (benzyloxycarbonyl)-L-glutamyl-L-alanyl-L-tyrosyl-glycyl-L-tryptophyl-L -methionyl-L-aspartic acid amide were prepared and were shown to competitively inhibit the binding of labeled human gastrin to its receptors in an isolated gastric mucosal cell preparation and to antagonize the action of gastrin on gastric acid secretion (ED50 from 1.5 to 7 mg/kg) in vivo in the reperfused rat stomach, determined according to the method of Ghosh and Schild. From these studies, it could be concluded that the C-terminal phenylalanine residue, which is of primary importance for intrinsic biological gastrin-like activity, is not essential for binding to gastrin receptors.

Ac-[3- and 4-alkylthioproline31]-CCK4 analogs: synthesis and implications for the CCK-B receptor-bound conformation.

It has been reported that substitution of the Met31 residue in Boc-CCK4 (Boc-Trp30-Met31-Asp32-Phe33-NH2, CCK33 numbering) by trans-3-propyl-L-proline yields a highly potent and selective CCK-B agonist. To further explore the structural requirements of the Met31 side chain in the receptor-bound conformation of CCK4, we have synthesized several Ac-CCK4 analogs containing substitution of Met31 by 3- and 4-(alkylthio)-substituted proline derivatives. To this end we have developed novel synthetic routes to enantiomerically pure N-Boc-4-cis- and -trans-(methylthio)prolines and racemic N-Boc-3-cis and -trans-[(4-methylbenzyl)thio]prolines. The protected mercaptoprolines were incorporated into Ac-CCK4 analogs using SPPS and were alkylated using various electrophiles following cleavage from the solid support. Binding assays reveal that 3-(alkylthio)prolines analogs have higher affinities at the CCK-B receptor than the corresponding 4-(alkylthio)proline analogs, and that trans-3-(alkylthio)proline analogs had higher affinities than corresponding cis-3-(alkylthio)proline analogs. Within both the cis- and trans-3-(alkylthio)proline series, the order of potency was found to be Me < Et < n-Pr. The trans-3-(n-propylthio)-L-proline analog demonstrates a higher affinity than that reported for Boc-CCK4[trans-3-propyl-L-Pro31]. Comparison of the low-energy structures calculated for several high-affinity Ac-CCK4 analogs reveal a common geometry which we propose to be the CCK-B receptor-bound conformation. This model shows grouping of the hydrophobic side chains of Trp, Met, and Phe at one side of the molecule and the hydrophilic side chain of Asp and the C-terminal carboxamide at the other side.

Synthesis and biological activities of pseudopeptide analogues of the C-terminal heptapeptide of cholecystokinin. On the importance of the peptide bonds.

A series of pseudopeptide analogues of the C-terminal heptapeptide of cholecystokinin in which each peptide bond, one at a time, has been replaced by a CH2NH bond were synthesized: Z-Tyr(SO3-)-Nle-Gly-Trp-Nle-Asp psi-(CH2NH)Phe-NH2 (1), Z-Tyr(SO3-)-Nle-Gly-Trp-Nle psi (CH2NH)Asp-Phe-NH2 (2), Z-Tyr(SO3-)-Nle-Gly-Trp psi-(CH2NH)Nle-Asp-Phe-NH2 (3), Z-Tyr(SO3-)-Nle-Gly psi(CH2NH)Trp-Nle-Asp-Phe-NH2 (4), Z-Tyr(SO3-)-Nle psi-(CH2NH)Gly-Trp-Nle-Asp-Phe-NH2 (5), Z-Tyr(SO3-)-Met-Gly-Trp-Nle-Asp psi (CH2NH)Phe-NH2 (6), Z-Tyr-(SO3-)-Met-Gly-Trp-Nle psi (CH2NH)Asp-Phe-NH2 (7), Z-Tyr(SO3-)-Met-Gly-Trp psi (CH2NH)Nle-Asp-Phe-NH2 (8). These derivatives were studied for their ability to stimulate amylase release from rat pancreatic acini and to inhibit the binding of labeled CCK-9 to rat pancreatic acini and to guinea pig brain membrane CCK receptors. They were compared to the potent CCK-8 analogue Boc-Asp-Tyr(SO3-)-Nle-Gly-Trp-Nle-Asp-Phe-NH2. All of these pseudopeptides were able to stimulate amylase secretion with the same efficacy as CCK-8 but with varying potencies. These compounds were also potent in inhibiting the binding of labeled CCK-9 to CCK receptors from rat pancreatic acini and from guinea pig brain membranes.

Synthesis and biological evaluation of cholecystokinin analogs in which the Asp-Phe-NH2 moiety has been replaced by a 3-amino-7-phenylheptanoic acid or a 3-amino-6-(phenyloxy)hexanoic acid.

Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester (JMV180), an analog of the C-terminal octapeptide of cholecystokinin (CCK-8), shows interesting biological activities behaving as an agonist at the high-affinity CCK binding sites and as an antagonist at the low-affinity CCK binding sites in rat pancreatic acini. Although we did not observe any major hydrolysis of the ester bond of Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester in our in vitro studies, we were aware of a possible and rapid cleavage of this ester bond during in vivo studies. To improve the stability of Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester, we decided to synthesize analogs in which the ester bond would be replaced by a carba (CH2-CH2) linkage. We synthesized the 3-amino-7-phenylheptanoic acid (beta-homo-Aph) with the R configuration in order to mimic the Asp-2-phenylethyl ester moiety and the 3-amino-6-(phenyloxy)hexanoic acid (H-beta-homo-App-OH), an analog of H-beta-homo-Aph-OH in which a methylene group has been replaced by an oxygen. (R)-beta-Homo-Aph and (R)-H-beta-homo-App-OH were introduced in the CCK-8 sequence to produce Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-(R)-beta-homo-Aph-OH and Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-(R)-beta-homo-App-OH. Both compounds were able to recognize the CCK receptor on rat pancreatic acini (IC50 = 12 +/- 8 nM and 13 +/- 5 nM, respectively), on brain membranes (IC50 = 32 +/- 2 nM and 57 +/- 5 nM, respectively), and on Jurkat T cells (IC50 = 75 +/- 15 nM and 65 +/- 21 nM, respectively). Like Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester, both compounds produced maximal stimulation of amylase secretion (EC50 = 6 +/- 2 nM and 4 +/- 2 nM, respectively) with no decrease of the secretion at high concentration indicating that these compounds probably act as agonists at the high-affinity peripheral CCK-receptor and as antagonists at the low-affinity CCK-receptor. Replacing the tryptophan by a D-tryptophan in such analogs produced full CCK-receptor antagonists. All these analogs might be more suitable for in vivo studies than Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester.

Structure-activity relationships of C-terminal tri- and tetrapeptide fragments that inhibit gastrin activity.

A series of tri- and tetrapeptide derivatives, analogues of the gastrin C-terminal region with no phenylalanine residue, were synthesized. These peptides were tested for their ability to inhibit gastrin-stimulated acid secretion in vivo as well as binding of [125I]-(Nle11)-HG-13 to gastric mucosal cell receptors in vitro. Most of the peptides tested exhibited gastrin antagonist activity in vivo and in vitro. Most active derivatives were 20-30 times more potent than the well-known gastrin antagonist derivatives proglumide and benzotript and had 20-200 times more binding affinity. The smallest fragment exhibiting antagonist activity was the tripeptide Boc-L-tryptophyl-L-methionyl-L-aspartic acid amide.

Large and prolonged in vivo response of pancreatic secretion to phenylethylamide and phenylethylester derivatives of Boc-[Nle28-Nle31]CCK(26-33) in the rat.

Supramaximal doses of cholecystokinin (CCK) induce in vitro submaximal biological responses (i.e., smaller by 50% than the response to a maximal dose of CCK), desensitization and residual stimulation, and in vivo secretory inhibition and edematous pancreatitis. It has been reported previously that supramaximal doses of Boc-[Nle28-Nle31]CCK(27-32)/- phenylethylester (JMV 180) do not produce these effects. The aim of this study was to analyze the in vivo response of pancreatic secretion of the rat to a wide dose range of Boc-[Nle28-Nle31]CCK(26-33) (JMV118), an analog of CCK8 with the same activity spectrum as CCK8, to JMV180 and to Boc-[Nle28-Nle31]CCK(27-32)-phenylethylamide (JMV170). The three peptides were administered as intravenous infusions and as bolus intravenous injections. In the case of infusions, the same maximal effect was observed with all three peptides. It was obtained with 22.5 pmol/kg.min of JMV118; JMV180 and JMV170 were about 700 times less potent. In the case of bolus injections, the maximal response to JMV118 was observed with 450 pmol/kg, and the response peaked 10-15 min after the injection. Higher doses of JMV118 induced a secretory peak that was smaller and delayed relative to the moment of injection. JMV180 and JMV170 were about 500 times less potent: the maximal response was observed with 218700 pmol/kg and peaked 10-15 min after the injection. Larger doses of JMV180 and JMV170 produced neither supramaximal inhibition nor a delayed peak response, but induced a sustained stimulation of pancreatic secretion that could last more than 3 h after the injection.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of the Asp-32 residue of cholecystokinin in gastric acid secretion and gastrin receptor recognition.

The aspartic acid residue at the penultimate position is known to be essential for the hormonal activity of CCK and gastrin on gastric acid secretion. This residue was successively replaced by beta-aspartic acid, beta-alanine, and glutamic acid in the C-terminal heptapeptide of CCK 27-33. The analogues obtained were tested on rat gastric acid secretion and for recognition by gastrin receptors. The replacement by beta-aspartic or beta-alanine decreased gastric secretion and gastrin receptor recognition. In contrast, replacement by glutamic acid affected these two parameters less. The nature of the N-blocking group (Boc or Z) also influenced these activities, Boc derivatives being more potent than Z derivatives. The results were compared to those previously obtained on pancreatic secretion and on stimulation of gall bladder contraction where the modifications were found capable of differentiating between cholecystokinin, pancreozymin and gastrin activities.

Pharmacological profile of a new peptidic gastrin antagonist.

Boc-Trp-Met-Asp-NH2 was described as the smallest peptidic fragment which presented gastric antisecretory activity. Some pharmacological aspects of a peptide analogue, Boc-Trp-Leu-Asp-NH2 (Boc-WLD-NH2), were studied on the main biological functions of gastrin. This compound was found to inhibit the binding of gastrin to isolated gastric fundic mucosal cells (IC50 50 microM). On pentagastrin-induced gastric acid secretion in the rat, a dose-dependent inhibition was observed with an ID50 of 55 mumol/kg when pentagastrin (1 microgram/kg per h) was continuously infused and with an ID50 of 7.8 mumol/kg when pentagastrin (1 microgram/kg) was bolus i.v. injected. Similar inhibition was observed on acid secretion induced by pentagastrin in the isolated rat gastric mucosa (IC50 100 microM), whereas the tripeptide had no effect when acid output was triggered by histamine. A dose-dependent inhibition with the tripeptide was shown on pentagastrin induced guinea-pig ileum contractions (IC50 31 microM). The compound had no activity on histamine-stimulated guinea-pig atria (histamine H2-receptor). These results suggest some evidence for a selective antigastrin activity.

Cholecystokinin increases intracellular Ca2+ concentration in the Human JURKAT T Lymphocyte cell line.

We have recently demonstrated the presence of specific high-affinity cholecystokinin binding sites of the central type on the Human JURKAT T Lymphocyte Cell line. In this paper, changes in intracellular Ca2+ concentration ([Ca2+]i) in response to CCK (cholecystokinin) peptides were measured in the Human JURKAT T Lymphocyte Cell line by fura-2 fluorometry. CCK-8 (the C-terminal octapeptide of CCK), the potent CCK analog Boc-[Nle28,31]CCK-7, stimulated ([Ca2+]i) mobilization in a dose-dependent manner in cells preloaded with fura-2 AM with an EC50 of 2.4 +/- 1 nM and 8 +/- 2 nM, respectively. The selective CCKB receptor agonists, namely Boc-Trp-Nle-Asp-Phe-NH2 and the cyclic analog JMV320, [formula: see text], were also potent in stimulating mobilization of [Ca2+]i with an EC50 of 32 +/- 10 nM and 25 +/- 10 nM, respectively. Compound JMV180, Boc-Tyr(SO3H)-Nle-Trp-Nle-Asp-2-phenylethyl ester, did not stimulate [Ca2+]i but inhibited the mobilization of [Ca2+]i elicited by 10 nM CCK-8 in a dose-dependent manner with an IC50 of 10 +/- 2 nM. The selective non-peptide CCKB receptor antagonist L-365,260 was more potent than the selective CCKA receptor antagonist MK-329 in inhibiting the [Ca2+]i mobilization elicited by 10 nM CCK-8 with IC50 values of 20 +/- 8 nM and 400 +/- 100 nM, respectively. These data indicated that CCK-8 and potent CCK analogs induced [Ca2+]i mobilization in the Human JURKAT T cell line through the CCKB/gastrin receptor type.

Synthetic CCK8 analogs with antagonist activity on pancreatic receptors: in vivo study in the rat, compared to non-peptidic antagonists.

The cholecystokinin octapeptide (CCK8)-derived synthetic peptides Boc-Tyr(SO3H)-Nle-Gly-DTrp-Nle-Asp-O-CH2-CH2-C6H5 (JMV179) and Boc-Tyr(SO3H)-Nle-Gly-DTrp-Nle-Asp-NH-CH2-CH2-C6H5 (JMV167) are antagonists of peripheral cholecystokinin (CCK) receptors in vitro. In the present study, antagonist activity of these peptides was studied on rat pancreatic secretion in vivo, and compared to those of other peptidic molecules and to the non-peptidic antagonists L364718, D-, L-, DL-lorglumide, and proglumide. The decreasing order of antagonist potencies on amylase release in vitro was L364718 greater than JMV179 greater than lorglumide greater than JMV167 greater than proglumide; JMV179 was 25 times less potent than L364718 and 300 times more potent than JMV167. The decreasing order of antagonist potencies on protein output in pancreatic juice in vivo was L364718 greater than JMV167 greater than JMV179 greater than lorglumide greater than proglumide; JMV167 was two times more potent than JMV179 and only 8 times less potent than L364718. Increased potency of JMV167, relative to JMV179 under in vivo conditions, is probably due to the slower rate of catabolism of the phenylethylamide group, relative to the phenylethylester group, since the metabolite issued from hydrolysis of the ester bond was totally inactive. This study shows that it is possible to obtain peptidic CCK antagonists, which are active and potent in vivo, and provides a quantitative measurement of potency changes occurring in vivo for several peptidic and non-peptidic antagonists.

Pharmacological activity of cholecystokinin analogues modified in the Met28-Gly29 region.

Analogues of the C-terminal octapeptide of cholecystokinin (CCK) modified in the Met28-Gly29 region, were tested for their ability to interact with peripheral cholecystokinin receptors on rat pancreatic acini and to stimulate amylase secretion. These analogues were further evaluated for their ability to recognize central CCK receptors on guinea pig brain membranes. The behavioral effect of these analogues was also tested after intrastriatal injection into mice. It appeared that these analogues were full CCK agonists in the peripheral system. Although some induced dopaminomimetic effects after intrastriatal injection into mice, being as potent as the C-terminal octapeptide of cholecystokinin (CCK-8), others did not have any effect and were able to antagonize CCK-8 actions in the striatum. The results of this study confirm that one can obtain very potent CCK analogues by modifying the peptide bond between Met28 and Gly29, and that this modification can produce either CCK agonists or antagonists of CCK-induced dopamine transmission in the striatum.

Cholecystokinin and gastrin are not equally sensitive to GTP gamma S at CCKB receptors: importance of the sulphated tyrosine.

We have shown that gastrin and cholecystokinin octapeptide (CCK-8) are differently coupled to G protein (GTP-binding protein) through type B cholecystokinin receptors in guinea-pig brain membranes and Jurkat cells. Indeed, the gastrin-13 binding affinity is strongly reduced by stable guanyl nucleotides, whereas CCK-8 binding is only slightly affected. In order to determine the structural requirements regulating such coupling, we have synthesized several gastrin and cholecystokinin fragments (sulphated or unsulphated) elongated at the N-terminus of the common C-terminal tetrapeptide. We investigated their interaction with CCKB receptors in guinea pig brain membranes and Jurkat cells and their involvement in the G protein coupling. Their apparent binding affinities to CCKB receptors were measured by inhibition of [125I]Bolton Hunter-CCK-8 (3-[125I]iodo-4-hydroxyphenyl)propionyl-CCK-8) binding in the presence or absence of GTP gamma S (guanosine 5'-O-(3-thio)triphosphate) or aluminum tetrafluoride (AlF4-). Activation of the G proteins by GTP gamma S or AlF4- led to a decrease in binding affinity for the gastrin related peptides, the common CCK-gastrin C-terminal forms, the cholecystokinin hexapeptide and the unsulphated cholecystokinin heptapeptide. Sulphated CCK-7, CCK-8, and cionin apparent binding affinities were not affected. These finding indicated that the sulphated tyrosine in position 7 in CCK (as counted from the C-terminus), provides the cholecystokinin selectivity for the CCKB receptor compared to gastrin. The results are discussed with the aim to better clarify the physiological relevance of gastrin and cholecystokinin toward CCKB receptors and their related intracellular events.

Pharmacological characterization of new cholecystokinin analogues.

New analogues of cholecystokinin-7 (CCK-7) modified at amino acid residues 5 and 7 were assayed for their effect on gall bladder, pancreatic secretion, food intake (anorectic activity), amount of rearing (sedative activity) and analgesia, as well as their ability to inhibit 125I-CCK-8 binding to pancreatic cell membrane receptors and brain membrane receptors. The results were compared to the activities of standard compounds, CCK-8, cerulein, BOC-CCK-7 (BOC = tertbutyloxycarbonyl) and BOC-[Nle2,Nle5]CCK-7. All analogues exhibited agonistic effects. Their anorectic activity was significantly prolonged.

[Structure-activity relationship of cystokinins: analogs exhibiting selective activity]. / Relations structure-activité de la cholécystokinine: analogues présentant des activités sélectives.

Structure-activity relationship on cholecystokinin is presented. C-terminal heptapeptide analogues of cholecystokinin exhibiting selective agonist or antagonist activities were synthesized and their biological and pharmacological properties studied. We showed that: 1) Suppression of the C-terminal phenylalanine residue leads to peripheral as well as central cholecystokinin receptor antagonists; 2) Suppression of the C-terminal amide function produces "partial agonists" exhibiting interesting biological and pharmacological activities; 3) Replacement of L-tryptophan residue by D-tryptophan in such "partial agonist analogues" resulted in potent CCK receptor antagonists; 4) The peptide bond between methionine28 and glycine29, as well as the glycine residue are quite significant for the central biological activity; 5) It is possible to obtain highly potent and selective CCK analogues for the central receptor (CCK-B) by cyclization including the C-terminal tetrapeptide. Synthesis and pharmacological studies with these analogues have allowed to precise the significance of some amino acid residues as well as of some peptide bonds. They are significant pharmacological tools for the study of CCK-A (peripheral) and CCK-B (central) receptors, their biological actions and their associated intracellular messengers.